The present invention relates to a process and a device for mechanically flushing storage containers with gases.
The preservation of stored degradable food products on a scale permitting mass consumption has presented problems to manufacturers since canned meat and vegetables were first introduced to British consumers in about 1818. One cause of persistent problems in uniformly preserving stored foods on a scale of mass consumption, ironically, includes a steady development of new food products. The new food products have required new processes and devices for preserving the products during storage. Unfortunately, the development of new processes and devices for food storage has, in some instances, lagged behind new product development. Consequently, existing processes and devices have been enlisted to store the new products. Because the existing processes and devices do not optimally preserve the new products, the existing storage processes and devices cause preservation problems.
The processes and devices employed to preserve the stored food products are typically directed to degradation problems that are common to both existing food products and to new food products. For instance, many kinds of food products are rendered unpalatable by undesirable oxidation reactions occurring during storage. The oxidation reactions may occur as a result of a prolonged exposure of the food to air. For many types of food products then, preservation during storage hinges on whether air is adequately removed from a storage container prior to sealing food into the container.
For some types of food products, food quality is enhanced by creating and maintaining particular gas compositions within a storage container. The gas compositions may be evolved by the food product itself or may be added to the product prior to storage.
One method for removing air from a container storing food has included applying a vacuum to the food container to displace the air. Once air is displaced, the food container may remain under vacuum or be backflushed with a desired gas or gas composition. A vacuum may be applied by heating the food and a sealable container, thereby driving air out of the container and cooling the food and container so that the container is sealed during cooling. A vacuum may also be applied by mechanically pulling the air out of the container. The appropriate method of applying a vacuum depends upon the type of food to be stored and upon whether the food can withstand the conditions of particular vacuum generating methods.
Air removal by a generation of a vacuum tends to be excessively time consuming. Additionally, backflushing adds more time. Further, some storage containers won't retain a vacuum. Both heating and cooling to generate a vacuum and mechanical generation of a vacuum to evacuate air require a substantial number of steps. The steps have a significant time requirement for completion.
The generation of a vacuum to evacuate air also tends to be expensive because it requires specialized equipment and substantial energy to generate heat in order to drive air out of the storage container. Additionally, methods relying on a generation of a vacuum lack versatility. Thus, the methods are not easily adaptable to new foods having characteristics that can be damaged in the generation of a vacuum. Further, air removal by imposition of a vacuum tends to yield variable results.
In addition to evacuating air by vacuum, air removal methods have also included sparging air from a headspace of food storage containers with a charge of a sparging gas. However, existing air sparging processes have tended to be time consuming. Additionally, sparging the headspace of a dough product has required a substantial amount of sparging gas to reduce gas concentration. For instance, for a container storing dough having a headspace of about 50 cubic centimeters, about 500 cubic centimeters of flushing gas are required to reduce oxygen in the headspace from about 20 percent to 2 percent.